1. Field of the Invention
The present invention relates to an apparatus using sampling/resolution conversion capable of converting conversion encoding coefficients rapidly and precisely.
2. Description of the Related Art
As one of related arts of this kind, there is a method (first method, hereinafter) in which information is completely decoded and then re-encoded. In this first method, after the encoded information is once decoded completely and is converted from 4:1:1 format into 4:2:0 format for example, resolution thereof is changed and then, the information is re-encoded.
As another related art, there is proposed a method (second method, hereinafter) in which encoding is again utilized as described in Japanese Patent Application Laid-open No.2001-136527. In this second method, after 4×4 element is extracted from coefficients which is encoded in 8×8 unit, it is decoded on the assumption that it is encoded in 4×4 unit, and it is re-encoded to obtain conversion encoding coefficients.
According to the first method, however, it is necessary to completely decode the information and to re-encode the same, and a sampling mode must be further converted. Therefore, there is a problem that an enormous computation amount is required and the processing speed is reduced. There is also a problem that since an enormous amount decoded data must be temporality stored, a large-capacity data region is required.
Since the second method re-utilizes the encoded information, the processing speed is faster than that of the first method. However, since the information is decoded in orthogonal basis different from that used for the conversion encoding, there is a problem that the information is largely deteriorated and sufficient image quality can not be obtained. Further, since the second method is based on the assumption that only pixels are obtained by resolution conversion, it is necessary to separately convert the sampling in a pixel region like the first method.